Significance and impact of proposed research. There are many associated with the management of blood stream infections caused especially by A. fumigatus and Candida species. It is clear from the literature that part of the problem is associated with the lack of new drug therapies that do not select for drug-resistant strains and that are free of toxicity or drug-drug interactions. There are two points of interest in regard to our proposal. First, there are no new classes of anti- fungals;the new drugs are remodeled triazoles or echinocandins, many still not evaluated clinically. Second, in spite of the problems associated with AmpB that include toxicity and increased cost of the less toxic liposomal preparations of AmpB, this drug remains as the major fall back choice to fluconazole or an echinocandin in the non-neutropenic patient with candidemia. In this regard, voriconazole offers little advantage over fluconazole. The same unfortunate rationale is used for treating patients that are neutropenic. The impact of our studies is focused upon preliminary data that indicate high susceptibilities to our compounds among several Candida species, Aspergillus fumigatus, and C. neoformans. In fact, the minimum fungicidal concentration (MFC) of our compounds is equivalent to the minimal inhibitory concentration (MIC). This feature is certainly important in drug discovery. Of utmost importance, our compounds are inhibitory to fluconazole- and micafungin-resistant Candida species and Cryptococcus neoformans. These new data strongly show that our compounds have a unique target(s). Furthermore, our approach to target discovery now focuses upon a genetic analysis using yeast knock-out and over expression libraries. Proof-of-principle studies by other groups provide confidence for our experiments. The point is that there are few choices among anti-fungal drugs, and urgency has been suggested recently by leaders in fungal disease research to develop new treatments. We propose in specific aim 3 that ADME/TOX studies be done to demonstrate that our compounds have low toxicity to human cells. PUBLIC HEALTH RELEVANCE: Current therapies for the treatment of invasive fungal diseases such as candidiasis are few in number. Also, there are problems associated with the antifungal drugs used to treat patients. Those problems include toxicity either as a result of the drug itself or toxicity associated with drug-drug interactions. In addition, the use of triazole antifungals has resulted in a change in the spectrum of Candida species that cause candidiasis as these drugs select for more resistant strains. Thus, there are many complications associated with the management of blood stream infections caused especially by Candida species. The impact of our studies is focused upon preliminary data that indicate high susceptibilities and fungicidal activities of compounds generated by Dr. William Groutas, the Co-PI in this project. Working with Dr. Calderone, Dr. Groutas has shown that lead compounds have a minimum fungicidal concentration (MFC) that is equivalent to their minimal inhibitory concentration (MIC). This feature is certainly important in drug discovery. Importantly, the chemotype embodied in the hits is structurally distinct from all anti-fungal agents currently used in the clinic and in development. New data establish that our compounds inhibit a collection of over 20 fluconazole- and micafungin-resistant strains of C. glabrata, C. albicans, and Cryptococcus neofomans, proving that they are directed against unique targets compared to currently used anti-fungals. We intend to pursue target identification based upon genetic approaches that utilize yeast libraries of knock-out and overexpressed mutants. This is the most direct approach to solving questions about the identity of drug targets. Further new lead compound identification is in progress, and ADME/TOX studies are included in the current proposal. The long term goal of this program is the development of novel therapeutics against fungal infection with superior characteristics by advancing the 1, 2-benzisothiazolin-2(3H)-one series of compounds through the stage prior to filing for an investigational new drug (IND) application.